# Units of solid angle

## Homework Statement

What are the units of solid angle in other systems ( In SI, it is steradian)

## The Attempt at a Solution

Hootenanny
Staff Emeritus
Gold Member
The solid angle is technically dimensionless, i.e. it has no real units. It is simply 'assigned' the SI unit of 'steradian' to distinguish it from other dimensionless quantities, such as constants etc.

Therefore, the solid angle has no alternative units other than SI.

HallsofIvy
Homework Helper
The first thing I did was use good old "Google" which sent me to Wikipedia:
http://en.wikipedia.org/wiki/Solid_angle
where I learned that the corresponding units are "square degree" and "fractional area" (what fraction of a circle does it subtend?).

I agree with Hootenanny that a solid angle (like any angle) is dimensionless but it appears there are other "assigned" units.

Hootenanny
Staff Emeritus